This invention relates to a dosimeter and in particular to a dosimeter designed for monitoring working areas.
Dosimeters are known and have been used in an effort to determine the level of exposure of workers to foreign substances in air, for example, to chemical vapors or fumes, dust particles and the like. A dosimeter is placed in a work area and air is pumped through a filter which traps foreign substances in the air. At the end of an exposure period, the filter is removed and analyzed for any foreign substances. One problem with these dosimeters has been that the air flow rate through the dosimeter has not been accurately controlled at a constant flow rate. For example, if the filter is partially blocked so that intake of air is momentarily stopped or reduced for a period of time, it is not possible to adjust and increase the flow rate of air to compensate for the stoppage or reduction of air passing through the filter of the dosimeter. Any reduction in the air flow rate reduces the amount of foreign substances collected by the filter thereby giving an inaccurate reading.